Extrapolation of the Satellite Altimeter Record to Understand Regional Variations in Future Sea Level Change

Abstract We perform a quadratic extrapolation of sea level on a regional scale based on satellite altimeter observations spanning 1993.0–2023.0, including corrections for natural climate variability, vertical land motion, and a rigorous assessment of the uncertainties associated with serially correlated formal errors, glacial isostatic adjustment, and satellite altimeter measurement errors. The extrapolations are data‐driven and show the trajectory of relative sea level (RSL) over the last 30 years extrapolated into the future. These extrapolations suggest that RSL rise in 2050 relative to 2020 will be 22 ± 5 cm in the North Pacific, 19 ± 6 cm in the North Atlantic, 17 ± 4 cm in the South Atlantic, 15 ± 5 cm in the Indian Ocean, 14 ± 5 cm in the South Pacific, 13 ± 5 cm in the Tropical Pacific, and 12 ± 4 cm in the Southern Ocean. The regional results may differ from each other by more than 80% and differ significantly from the extrapolated global mean sea level rise of 16 ± 4 cm in most cases. The errors in these regional extrapolations are relatively narrow, and we show significant overlap with the regional projections from the most recent IPCC Sixth Assessment Report. The results provide an additional line of evidence when considering how representative the range of climate model projections are in describing near‐term sea level rise and highlight the significance of regional variations in estimates of future sea level.